The present invention relates to a reed switch with high insulation for a very low current measurement system.
Previously, Takuo Banno has indicated in Japanese Utility Model Laid-Open No. 57-131743, which has been assigned to Yokogawa-Hewlett-Packard Co., Ltd., that there is an unfavorable effect on signals caused by insulation resistance of switches, especially when measuring very low amplitude signals. Therefore, in the above-named Japanese Utility Model, Banno has proposed a particular combination of multiple switches to avoid such effects. When a reed switch is used as said switch, the resistivity of its insulation may generally be only approximately 10.sup.9 .OMEGA. in a non-hostile environment, because of the leakage current on its glass-made surface. For very low current measurement, such order of insulation resistance is too low for measurement as is also suggested by Banno in the aforementioned Japanese Utility Model.
Improved insulation resistance of a reed switch could be achieved by washing or silicon coating. However, such treatment may not be effective for very low current measurement under high temperature and humid conditions in which its insulation resistance could still be less than 10.sup.12 .OMEGA..
A primary object of the present invention is to provide a reed switch with high insulation which can be used as matrix switches and scanners for very low current measurement even under high temperature and humid conditions.